The invention relates to a method and device for detecting a viewing direction of a person, for example, of a driver in a motor vehicle.
Determining the viewing direction of a driver of a motor vehicle may be used for various driver assistance functions. For example, the display of the head-up display can be adapted or tracked as a function of the driver's viewing direction so that important information can be provided to the driver without any movements of the driver's eyes or head.
Moreover, warning devices can be provided which, as a result of analyzing the driver's viewing direction, detect when the driver, for an extended time period, looks away from a traffic situation lying ahead, for example, when the driver is looking at an instrument panel, or is searching for an object in the interior of the occupant compartment, etc.
German Patent Document DE 199 51 001 A1 discloses a device that allows information from various data sources is faded into the driver's field of view based on a driver's viewing direction.
Various methods are known for determining a driver's viewing direction. For example, by way of an infrared camera and an infrared light beam, by measuring the position of an infrared reflex point on the driver's pupil, the position of the iris can be detected and a viewing direction can be derived therefrom.
Another method uses an optical pattern detection in order to detect the boundary between the sclera and the iris of the eye and derive a viewing direction of the eye.
Determination methods are known that are based on the reflection of a light beam in the eye. For example, several reflection points in the eye can be captured at different optical interfaces. The alignment of the eye may thereby be detected and the viewing direction may be derived therefrom. This method is called the Purkinje Method.
Moreover, eye-tracking methods are known, in which with several cameras, a surface of the pupil of an eye as well as the normal vector standing thereon are calculated, which essentially corresponds to the viewing direction or from which the viewing direction can be derived.
The above-known methods use camera systems in the infrared range for detecting the viewing direction. In that regard, these methods are susceptible to interferences, for example in unfavorable backlight or changing light situations, as they may occur, for example, when driving through tunnels and on semi-shady roads. Moreover, the calibration of previous systems requires high expenditures, particularly if these systems operate via an infrared reflection point on the eye.
It is therefore an object of the present invention to provide an improved, less interference-sensitive determination of a viewing direction that avoids the disadvantages of the state of the art and is suitable for use in a motor vehicle.
According to one aspect of the disclosure, a method is provided for determining a viewing direction of a person, for example, a driver in a motor vehicle. The method includes acquiring a surface contour of a surface of the person's eye, detecting a normal vector on the surface of the eye as a function of the acquired surface contour, and determining the viewing direction of the person as a function of the normal vector.
For example, the above-described method may include three-dimensionally acquiring the visible portion of an eye and determining a normal vector from the determined surface structure of the pupil, from which a driver's viewing direction can be derived. As a result, a low-interference determination of the driver's viewing direction can be implemented since this method is not based on an acquisition of a reflection point in the eye. In addition, acquisition of the surface contour of the eye offers may increase, in connection with other viewing direction detection methods, the precision and availability of a viewing direction specification. Calibration expenditures can also be reduced by the combination with another viewing direction detection method.
In accordance with one embodiment of the disclosure, the acquisition of the surface contour of the surface of the person's eye may be carried out via a depth sensor, for example, a TOF camera or a LIDAR sensor.
By way of example, the normal vector is determined as a function of a pupil region determined from the surface contour and a curvature of the pupil region. For instance, the pupil region may be determined as an elevation on the surface of the eye. The elevation may project beyond a spherical surface of an eyeball of the eye.
By way of another example, the normal vector is detected at the center of the pupil region as a function of the curvature at the center of the pupil region.
In accordance with an embodiment of the disclosure, the acquisition of the surface contour of the surface of the eye may be carried out via another camera by first acquiring the position of the eye and acquiring the surface contour by the position of the eye.
In yet another example, the viewing direction is determined by applying one or two predefined correction angles or determined by calibration to the normal vector, which may be the optical visual axis, in which instance, the one or more correction angle(s) is/are determined by way of a calibration method.
In accordance with another embodiment, a viewing direction detection system is provided for determining a viewing direction of a person, for example, a driver in a motor vehicle. The viewing direction detection system may include a depth sensor for acquiring a surface contour of a surface of the person's eye, a control unit that determines a normal vector on the surface of the eye as a function of the acquired surface contour and/or determines the person's viewing direction as a function of the normal vector.
Moreover, the viewing direction detection system may include an additional device for determining the person's viewing direction, in which instance the control unit may be configured to make the viewing direction plausible and/or merging it by way of a further viewing direction acquired by the additional device.
According to a further aspect, a use of the viewing direction detection system in a motor vehicle is provided in order to detect a viewing direction of a driver of the motor vehicle.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.